One type of well known juice extractor includes a series of juice extractor units that are ganged together. Each juice extractor unit includes upper and lower cups for supporting the fruit. The sides of both upper and lower cups have fingers that intermesh or interdigitate together. The upper cups are mounted on a common cross bar, which moves in a fixed up and down path by means of a cam-drive positioned at the top of the juice extractor machine. The upper cups move into the bottom cups, which remain rigidly positioned.
A fruit, such as an orange, is initially fed into the bottom cup by a cam-operated feeding device, which deposits the fruit in the bottom cup. The upper cup then descends into the lower cup. The fruit is pressed against sharp circular cutters positioned at the top of a strainer tube adjacent the lower cup, and an upper cutter positioned in the upper cup. The two circular cutters cut plugs into both the top and bottom portions of the fruit as the interdigitating fingers of the two cups mesh together. At the same time, the inner portions of the fruit (i.e., the pulp and juice) are forced down into the strainer tube positioned within a manifold. The peeled surfaces of the fruit do not contact the juice as the interdigitating fingers peel the fruit. After the upper cup has descended toward the lower cup, an orifice tube moves upward into the strainer tube. The prior art orifice tube includes a restrictor in its lower end. The orifice tube applies pressure into the internal portion of the strainer tube to separate juice and pulp within the strainer tube, collect the core material and discharge the core material out of the bottom of the orifice tube. The core material typically includes membrane, seeds and peel plugs.
Instead of a restrictor, a valve assembly has been placed against the lower end of the orifice tube, and has been actuated by pneumatic pressure to open and close a valve, such as a piston and shaft, to allow core discharge. The pneumatic pressure applied a back pressure to the orifice tube. As the orifice tube was moved within the strainer tube, the valve was closed by the pneumatic pressure to aid in the extraction process. As core filled the orifice tube, the pressure in the orifice tube became greater than the applied pneumatic pressure and the valve opened, thus allowing discharge of core out of the lower end of the orifice tube.
However, this type of structure has several drawbacks. Air is compressable and as any piston or other assembly was vertically raised at high operating speeds, it sometimes caused a partial vacuum, and it was difficult to control the amount of force on any piston or other assembly. It is essential that every time a core of pulp was placed in the orifice tube during the extraction process, then some core should be removed from the lower end of the orifice tube. If the orifice tube should become clogged, however, such as commonly occurs when a milk weed pod or other similar structure becomes clogged, then no core is removed from the lower end of the orifice tube. As a result, a phenomena occurs called "exploding fruit." The juice cannot be removed from the strainer tube and, as the upper and lower cups are forced together, the fruit explodes. In a worst case scenario, the strainer tube can also explode, and thus, seeds and cores enters the juice and cause major quality problems.